1. Field of the Invention
The present invention relates to a lightweight setter. More particularly, it relates to a lightweight setter for a shelf assembly having a beam structure used to fire a formed honeycomb article.
2. Description of Related Art
Heretofore, as a ceramic material firing kiln tool plate used during the firing of an article to be fired such as a formed honeycomb article, there has been known a ceramic material firing kiln tool plate which comes in contact with the article to be fired and which has a plate shape.
However, when the article to be fired is mounted and fired on the ceramic material firing kiln tool plate having the plate shape, a binder gas included in the article to be fired is not easily discharged, thereby causing a problem that a temperature difference occurs in a product to generate a breakage defect, or another problem that a binder residue during the firing hampers sintering to generate the breakage defect.
Moreover, owing to a large contact area, the binder gas is not easily discharged. In addition, the contact with an atmospheric gas becomes insufficient during the firing, and hence the atmosphere is confined, with the result that the breakage defect is generated. Furthermore, the article is deformed owing to contraction during the sintering to generate the breakage defect. The article easily adheres to a setter owing to the contraction during the sintering, which also generates a problem such as a crack or breakage defect.
To solve such problems, Patent Documents 1 to 3 are suggested as follows.
Patent Document 1 employs a firing kiln tool plate in which a ceramic porous material having pore diameters of about 0.5 to 4 mm is disposed as a supporter, and a surface layer of a surface-like ceramic porous material having bore diameters of 0.5 mm or less is formed on one surface of the supporter. In consequence, a gas permeability to a decomposed gas or the like generated from a lightweight half-finished product is secured, and the thermal strain of the finished product is prevented. In Patent Document 1, however, the ratio of the weight of a kiln tool with respect to a product weight is large, and a large loss takes place from the aspect of energy saving. Moreover, the binder gas is not sufficiently discharged during the firing, so that a temperature difference in the product still easily occurs, and a breakage defect is easily generated. Moreover, the atmosphere is easily confined, and the contact of the product with the atmospheric gas becomes insufficient during the firing, and the breakage defect is further easily generated. Therefore, any concrete countermeasure is not taken against the above problems.
Patent Document 2 is characterized in that a kiln tool plate is constituted of a base plate made of a ceramic material and a plurality of penetration holding portions provided on the ceramic base plate to separately hold electronic parts, respectively, and the shape of each of the penetration holding portions is tapered so that the sectional area thereof decreases from the upper surface to the lower surface. Moreover, the cross section of the penetration holding portion has such a size that at least the electronic part does not pass therethrough. The ceramic base plate of Patent Document 2 employs such a tapered shape that the sectional area decreases from the upper surface to the lower surface, to pass the atmospheric gas through all the holding portions, which is evaluated highly to a certain degree. However, the ratio of the weight of a kiln tool with respect to a product weight is large, a large loss is incurred from the aspect of energy saving, and a binder gas is not sufficiently discharged during firing. Moreover, owing to a large contact area with a product, the product is easily deformed owing to contraction during sintering, and might adhere to the ceramic base plate. In addition, the possibility of the occurrence of a fluctuation during manufacturing, for example, a crack or breakage defect, cannot be denied.
In Patent Document 3, a surface mount portion having an uneven surface structure is formed on the surface of a ceramic base member which comes in contact with an article to be fired, whereby the flow of hot air on a jig can be made uniform to uniformly fire the article to be fired. When such a constitution is employed, the flow of the hot air on the jig can be made uniform to a certain degree. The constitution is evaluated highly to a certain degree. However, it cannot be considered that a binder gas is sufficiently discharged during firing. Moreover, an atmospheric gas is easily confined. In addition, the ratio of the weight of a kiln tool with respect to a product weight is large, and a large loss is incurred from the aspect of energy saving. It cannot be considered that a countermeasure is sufficiently taken against deformation or the like due to contraction during sintering.
As described above, the above problems are not sufficiently solved at present, and a further improvement is demanded.
Patent Document 1: JP-A-5-17261
Patent Document 2: JP-A-6-45209
Patent Document 3: JP-A-6-281359